Releasing language parser plugins

Additional language parser plugins (in the /plugins folder) are released to pypi independently of Lute.

For example:

pushd plugins/lute-mandarin/
flit publish --repository pypi
popd

After releasing, do the regular release wrap-up.

Note: you probably also want the plug-in to be included in the lute image, so add it to docker/Dockerfile_scripts/install_everything.sh.